The invention relates to polypropylene brush bodies.
A toothbrush generally includes a body having a handle portion, a head portion and bristles extending from the head portion. The bristles can be arranged in the form of tufts. A toothbrush is constructed to withstand the normal pressures exerted upon the brush during brushing of teeth and other surfaces of the oral cavity.
Toothbrushes have been manufactured by injecting a liquid polymeric composition, e.g., polypropylene, into a mold cavity that defines a toothbrush body, whereupon the polymer composition hardens (i.e., freezes) in the form of the body of the toothbrush, e.g., the handle and head of the brush. For two component toothbrush bodies, the body of the toothbrush is then transferred to a second mold cavity and a second liquid polymer composition, e.g., an elastomer, is injected into the second mold cavity to form a second portion of the brush body, e.g., the gripping member.
The amount of time that it takes the liquid polymer composition to harden in the mold cavity is referred to as the xe2x80x9cset timexe2x80x9d. The xe2x80x9cset timexe2x80x9d influences the rate toothbrushes can be manufactured.
In one aspect, the invention features an oral brush that includes a body that includes a) a polymer composition that includes polypropylene and that has a melt flow rate of at least about 10 g/10 min, and b) a bristle extending from the body. In some embodiments, the body has a tensile strength of at least about 3100 psi. In other embodiments, the body has a tensile strength of at least about 3700 psi. The body can have a tensile strength of from about 3700 psi to about 6,000 psi.
In one embodiment, the body defines a shape that includes a handle and a head extending from said handle, where the handle includes a thumb grip having a cross-sectional area no greater than about 1.8 cm2. In other embodiments, the body defines a shape that includes a handle and a head extending from said handle, said handle having a cross-sectional area no greater than about 1 cm2.
In another embodiment, the polymer composition has a melt flow rate of from about 10 g/10 min to about 40 g/10 min. In some embodiments, the polymer composition has a melt flow rate of from about 15 g/10 min to about 30 g/10 min. In still other embodiments, the polypropylene has a melt flow rate of in the range of from about 30 g/10 min to about 40 g/10 min.
In one embodiment, the polypropylene has a tensile strength of from about 4000 psi to about 6000 psi.
In other embodiments, the polymer composition further includes a plastomer. In one embodiment, the plastomer has a melt flow rate of from about 1.3 g/10 min to about 5.2 g/10 min. The plastomer can have a tensile strength of from about 1500 to about 3100 psi. In some embodiments, the plastomer includes a copolymer that includes ethylene and a polyalpha-olefin. The polymer composition can include from about 2% by weight to about 30% by weight plastomer. In other embodiments, the polymer composition includes from about 10% by weight to about 20% by weight plastomer. In another embodiment, the polymer composition includes from about 75% by weight to about 90% by weight polypropylene, and from about 10% by weight to about 25% by weight of plastomer.
In another aspect, the invention features a process of manufacturing an oral brush body that includes injecting a polymer composition having a melt flow rate of at least 10 g/10 min into a mold cavity to form a body of the oral brush. In one embodiment the polymer composition includes polypropylene. In another embodiment, the polymer composition includes a plastomer. In other embodiments, the polymer composition further includes at least about 10% by weight of a plastomer. In another embodiment, the polymer composition includes polypropylene and a plastomer.
In one embodiment, the process further includes preparing the polymer composition by combining from about 75% by weight to about 90% by weight plastomer and from about 10% by weight to about 25% by weight polypropylene.
In other aspects, the invention features a process of manufacturing an oral brush that includes injecting a polymer composition having a melt flow rate of at least about 10 g/10 min into a mold cavity defining at least a portion of an oral brush body, the mold cavity that includes a plurality of bristles.
The oral brushes of the present invention are flexible and do not break when brushing forces are exerted gas on the head portion of the brush. In particular, the oral brushes do not break when flexed in a forward direction or a reverse direction. The brushes can also be returned to their original form after having been bent with this force.
The present invention enables the manufacture of brush bodies having relatively narrow regions that exhibit excellent resistance to breakage and remain flexible, yet are sufficiently rigid so as to provide a structure suitable for its intended purpose. In addition, because the brush bodies can be molded rapidly due to the minimal set time in the injection molding operation, excellent rates of production and manufacturing efficiencies are achieved.
Other features and advantages of the invention will become apparent from the following description of the preferred embodiments thereof, and from the claims.